The present invention relates to apparatus for abrading elongate workpieces such as lumber, and more particularly to an apparatus of the type utilizing a driven abrasive belt operable for planing the upper horizontal surface of a workpiece fed horizontally into contact with the belt.
Typical planing apparatus generally include one or more so-called hold down shoes which extend across a workpiece and urge it against a lower support or against a transporting conveyor as the workpiece is being fed horizontally into contact with the abrasive belt. In planing workpieces such as lumber, it is apparent that debris such as sawdust or chips are dislodged during abrading action. It is preferable to provide an exhaust duct or hood adjacent the area of contact of the abrasive belt with the lumber so that the debris may be immediately exhausted.
However, a problem arises in that prior art planing apparatus have not provided structure which adequately holds down the lumber while simultaneously exhausting debris. The problem arises from the fact that the lumber must be held down against a support closely adjacent to the point of lumber-belt contact. As a consequence, sufficient room for positioning an exhaust duct adjacent this point of contact simply has not been available. While hold down shoes have been located at a downstream position relative to the point of contact, such does not permit adequate holding down of the lumber adjacent its entry into contact with the abrasive belt.
Accordingly, it is a general object of the present invention to provide an abrading or planing apparatus in which a hold down shoe and exhaust duct are constructed as an integral assembly so that adequate holding down of the lumber and exhausting of debris can be simultaneously provided. More particularly, the present invention provides an assembly in which the hold-down shoe includes a member extending upwardly therefrom which forms a back wall of an entry duct.
Elaborating further, the entry duct includes an opening or mouth defined by a top wall member spaced apart from the hold down shoe. The top wall member is selectively positionable relative to the hold down shoe so that the cross-sectional area of the mouth may be selectively varied. As a result, the rate at which debris may be exhausted can correspondingly be varied.
Another object of the present invention is to provide an assembly, as described above, which may be readily mounted adjacent the frame of a planing apparatus and which includes biasing means operable for selectively pivoting the entry duct about a horizontal pivot axis. The axis extends generally transversely of the infeed direction of lumber conveyance and the biasing means includes a pair of cylinders having extendible-retractable rods.